Hydrolysis of poly(ethylene terephthalate) in a fluidised bed reactor

The hydrolysis of poly(ethylene terephthalate, PET) is the reverse of the direct esterification of terephthalic acid (TA) and ethylene glycol (EG). By this means the recovery of monomers is possible. These experiments have shown that 60%-72% of TA were recovered from virgin PET in a temperature range between 400 and 500°C. Another 22%-27% TA remained in oligomers. The highest yield of TA (72%) was found at 450°C. When real materials were used, still 60%-69% of TA were found at 450°C. There was also a catalytic effect of transition metal oxides which reduced the content of TA in oligomers to 8%. The yield of EG was less than 10% in all experiments. Most EG reacted with water to form carbon oxides and hydrogen. Other decomposition products were acetaldehyde and ethene.